On Tuesday, July 21, 2026 9:29:14 PM CEST Saverio Miroddi wrote:
> The ACPI specification defines OSC_CAPABILITIES_MASK_ERROR to mean that
> firmware cleared capability bits requested by the operating system. Some
> firmware sets this status during the control request while returning every
> requested capability unchanged. On the affected system, the requested and
> returned masks were both 0x006a7eff.
> 
> Commit e5322888e6bf ("ACPI: bus: Rework the handling of \_SB._OSC
> platform features") made all control-response errors produce error-level
> messages. Consequently, the inconsistent response above now claims that
> features may be missing even though none were removed.
> 
> Track whether the response actually clears a requested bit and omit the
> error-level messages only if OSC_CAPABILITIES_MASK_ERROR is the sole
> error and no capability was cleared. Keep the dynamic-debug diagnostic and
> leave the negotiated capability mask and all other error cases unchanged.
> 
> Fixes: e5322888e6bf ("ACPI: bus: Rework the handling of \_SB._OSC platform features")
> Signed-off-by: Saverio Miroddi <saverio.pub2@gmail.com>
> ---
>  drivers/acpi/bus.c | 23 ++++++++++++++++-------
>  1 file changed, 16 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> index a30a904f6535..c13128cbc2f6 100644
> --- a/drivers/acpi/bus.c
> +++ b/drivers/acpi/bus.c
> @@ -335,7 +335,8 @@ static int acpi_osc_handshake(acpi_handle handle, const char *uuid_str,
>  		.length = bufsize * sizeof(u32),
>  	};
>  	struct acpi_buffer output;
> -	u32 *retbuf, test;
> +	u32 *retbuf, test, errors;
> +	bool capabilities_masked = false;

The existing test variable can be used for this just fine, no need to add more
of them.

>  	guid_t guid;
>  	int ret, i;
>  
> @@ -395,16 +396,24 @@ static int acpi_osc_handshake(acpi_handle handle, const char *uuid_str,
>  	 * Clear the feature bits in capbuf[] that have not been acknowledged.
>  	 * After that, capbuf[] contains the resultant feature mask.
>  	 */
> -	for (i = OSC_QUERY_DWORD + 1; i < bufsize; i++)
> +	for (i = OSC_QUERY_DWORD + 1; i < bufsize; i++) {
> +		if (capbuf[i] & ~retbuf[i])
> +			capabilities_masked = true;
> +
>  		capbuf[i] &= retbuf[i];
> +	}
>  
> -	if (retbuf[OSC_QUERY_DWORD] & OSC_ERROR_MASK) {
> +	errors = retbuf[OSC_QUERY_DWORD] & OSC_ERROR_MASK;
> +	if (errors) {
>  		/*
> -		 * Complain about the unexpected errors and print diagnostic
> -		 * information related to them.
> +		 * Some firmware sets OSC_CAPABILITIES_MASK_ERROR without clearing
> +		 * any requested capability.  Only complain if another error is
> +		 * present or a capability was actually masked.
>  		 */
> -		acpi_handle_err(handle, "_OSC: errors while processing control request\n");
> -		acpi_handle_err(handle, "_OSC: some features may be missing\n");
> +		if (errors != OSC_CAPABILITIES_MASK_ERROR || capabilities_masked) {
> +			acpi_handle_err(handle, "_OSC: errors while processing control request\n");
> +			acpi_handle_err(handle, "_OSC: some features may be missing\n");
> +		}
>  		acpi_osc_error_check(handle, &guid, rev, &cap, retbuf);

And here the debug output is not quite useful if the error is essentially
ignored.

>  	}

So below is my version of this fix, please check it if works for you.

Thanks!

---
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Subject: [PATCH] ACPI: bus: Avoid confusing complaints regarding missing _OSC features

The platform firmware on some platforms sets OSC_CAPABILITIES_MASK_ERROR
in _OSC error bits even though it actually acknowledges all of the
requested features which after commit e5322888e6bf ("ACPI: bus: Rework
the handling of \_SB._OSC platform features") causes the kernel to
complain unnecessarily.

Avoid the confusing complaints by explicitly checking for that case
in acpi_osc_handshake().

Fixes: e5322888e6bf ("ACPI: bus: Rework the handling of \_SB._OSC platform features")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/bus.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -395,10 +395,18 @@ static int acpi_osc_handshake(acpi_handl
 	 * Clear the feature bits in capbuf[] that have not been acknowledged.
 	 * After that, capbuf[] contains the resultant feature mask.
 	 */
-	for (i = OSC_QUERY_DWORD + 1; i < bufsize; i++)
+	for (i = OSC_QUERY_DWORD + 1, test = 0; i < bufsize; i++) {
+		test |= capbuf[i] & ~retbuf[i];
 		capbuf[i] &= retbuf[i];
+	}
 
-	if (retbuf[OSC_QUERY_DWORD] & OSC_ERROR_MASK) {
+	/*
+	 * Some platforms set OSC_CAPABILITIES_MASK_ERROR even though they
+	 * acknowledge all of the requested features, so avoid complaining in
+	 * those cases unless any other error bits are also set.
+	 */
+	if ((retbuf[OSC_QUERY_DWORD] & OSC_ERROR_MASK) &&
+	    (test || retbuf[OSC_QUERY_DWORD] != OSC_CAPABILITIES_MASK_ERROR)) {
 		/*
 		 * Complain about the unexpected errors and print diagnostic
 		 * information related to them.

Hi!

I tested your version on the affected system.  The requested and returned
capability masks are both 0x006a7eff, and the two misleading error messages
no longer appear.  The negotiated capability masks are unchanged.

Tested-by: Saverio Miroddi <saverio.pub2@gmail.com>

Thanks!
Saverio